1. Field of the Invention
The invention relates to an optical analytical method and device and to a waveguide or optical fiber useful in the device.
2. Description of the Prior Art
U.S. Pat. No. 2,964,993 describes an apparatus for measuring fluids by analyzing the specific gravity or composition comprising a longitudinally extending radiant energy guide which is of a transparent radiant energy transmitting material such as sapphire, quartz or Pyrex.
U.S. Pat. No. 2,977,842 describes an apparatus and method for measuring the quantity of moisture in a moving sheet such as paper using fiber optics.
U.S. Pat. No. 3,071,038 describes a radiant energy measuring apparatus having a radiant energy transmitting light guide for obtaining a continuous accurate measurement of changes taking place in density and/or specific gravity of composition of a fluid that is flowing over the peripheral surface of this guide.
U.S. Pat. No. 3,370,502 describes an absorption cell means having a rod with a cell surrounding the rod, radiant energy being directed at one end of the rod means and passing down the rod with multiple internal reflection.
U.S. Pat. No. 3,409,404 teaches the optical properties of a cholesteric liquid crystalline material are changed when the cholesteric material is contacted with another material. A variety of materials, particularly vapors, are identified by observing their effect on cholesteric liquid crystalline materials. The most convenient observable effect is a change in the color of the cholesteric material and, if necessary, comparing the change effected by a known standard material. An anayltical device may comprise one or more distinct elements of cholesteric liquid crystalline material. Suitable cholesteric liquid crystalline materials include a wide variety of compounds, and mixtures thereof, derived from the cholesterol.
U.S. Pat. No. 3,752,584 describes a spectroscopic device and method of using attenuated total reflection techniques for analysis of samples of particulate solids in a fluid. A beam of radiation is passed through an optical cell comprising a plurality of elongated, totally internally reflecting elements, e.g., fiber optics arranged as a mechanical filter. When fluid containing the particles is passed transversely across the cell, the latter are trapped in the filter whereupon radiation passing through the elements is selectively absorbed, thus providing an optical output having an absorption spectrum which may be utilized to identify the sample.
U.S. Pat. No. 3,805,066 describes a smoke detecting device utilizing optical fibers with smoke paths in a series arrangement interrupting the light path.